Regulation of taste neuron morphology and function

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Project Summary: Taste-transducing cells detect chemicals in our food and communicate this information to peripheral taste ganglion neurons (taste neurons), which carry this information to the brain. The axons of taste neurons vary in branching characteristics, some branching little and others branching a great deal. However, it is unclear how these differing morphologies underly plasticity and/or function. Our goal here is to clarify the relationship between taste neuron morphology, plasticity, genetic type, and function in order to gain insight into the peripheral organization of the taste system. Taste neuron morphology may underlie differences in connectivity, but is also likely regulated by plasticity. Even in adults, taste receptor cells undergo continuous renewal and must constantly attract and connect to nerve fibers, and some variation in neuron morphology likely occurs as part of this process. Additionally, differences between neurons in their branching likely have functional importance. For example, simply branched neurons can only connect with a few taste-transducing cells, while heavily branched neurons likely connect to many more taste-transducing cells. Currently, the significance of these differences in convergence are unclear. In this project, we propose to investigate factors that regulate differences in taste neuron morphology and branching characteristics between neurons and relate these factors to neuron function. Specifically, in Aim 1, we will determine which aspects of the axon morphologies of taste neurons are stable and which change over time. In Aim 2, we will determine which aspects of neuron morphologies are determined by an intrinsic factor (i.e., cell type) and how this factor correlates with function. Finally, in Aim 3, we will determine which aspects of neuron morphologies are determined by extrinsic (i.e., neurotrophins) developmental factors and how these features relate to neuron function. We hypothesize that branching inside the taste bud is regulated by plasticity, while branching outside the taste bud is regulated by a combination of intrinsic and extrinsic features, which influence taste neuron sensitivity and breadth of tuning.